Low-flow push-pull perfusion is a sampling method that yields better spatial resolution than competitive methods like microdialysis. Because of the low flow rates used (50 nL/min) it is challenging to use this technique at high temporal resolution which requires methods of collecting, manipulating, and analyzing nanoliter samples. High temporal resolution also requires control of Taylor dispersion during sampling. To meet these challenges, push-pull perfusion was coupled with segmented flow to achieve in vivo sampling at 7 s temporal resolution at 50 nL/min flow rates. By further miniaturizing the probe inlet, sampling with 200 ms resolution at 30 nL/min (pull only) was demonstrated in vitro. Using this method, L-glutamate was monitored in the striatum of anesthetized rats. Up to 500 samples of 6 nL each were collected at 7 s intervals, segmented by an immiscible oil and stored in a capillary tube. The samples were assayed offline for L-glutamate at a rate of 15 samples/min by pumping them into a reagent addition tee fabricated from Teflon where reagents were added for a fluorescent enzyme assay. Fluorescence of the resulting plugs was monitored downstream. Microinjection of 70 mM potassium in physiological buffered saline evoked L-glutamate concentration transients that had an average maxima of 4.5 ± 1.1 μM (n = 6 animals, 3–4 injections each) and rise times of 22 ± 2 s. These results demonstrate that low-flow push-pull perfusion with segmented flow can be used for high temporal resolution chemical monitoring and in complex biological environments.
Interleukin (IL)-35 is a relatively newly discovered member of IL-12 cytokine family that is unique in that it is a dimer formed by two subunits. The review documents the structure, secretion and signal transduction of IL-35, the regulation effect of IL-35 on B cells and T cells as well as the adoptive transfer of IL-35+ regulatory B cells (Breg), therapeutic prospects of recombinant IL-35 (rIL-35) and IL-35 regulation role in various diseases. B-cell regulation expands the regulatory range of IL-35 and alters the view that IL-10 is the chief immune mechanism for Breg cells which secrete IL-35. IL-35 induces Breg cells, which then can induce Treg cells. IL-35 also plays an immunomodulatory role in the human body.
Methods for identifying chemical inhibitors of protein-protein interactions (PPIs) are often prone to discovery of false positives, particularly those caused by molecules that induce protein aggregation. Thus, there is interest in developing new platforms that might allow earlier identification of these problematic compounds. Capillary electrophoresis (CE) has been evaluated as a method to screen for PPI inhibitors using the challenging system of Hsp70 interacting with its co-chaperone Bag3. In the method, Hsp70 is labeled with a fluorophore, mixed with Bag3, and the resulting bound and free Hsp70 separated and detected by CE with laser-induced fluorescence detection. The method used a chemically modified CE capillary to prevent protein adsorption. Inhibitors of the Hsp70-Bag3 interaction were detected by observing a reduction in the bound to free ratio. The method was used to screen a library of 3,443 compounds and results compared to those from a flow cytometry protein interaction assay. CE was found to produce a lower hit rate with more compounds that reconfirmed in subsequent testing suggesting greater specificity. This finding was attributed to use of electropherograms to detect artifacts such as aggregators and to differences in protein modifications required to perform the different assays. Increases in throughput are required to make the CE method suitable for primary screens but at the current stage of development it is attractive as a secondary screen to test hits found by higher throughput methods.
A key challenge when imaging whole biomedical specimens is how to quickly obtain massive cellular information over a large field of view (FOV). We report a subvoxel light-sheet microscopy (SLSM) method enabling high-throughput volumetric imaging of mesoscale specimens at cellular resolution. A nonaxial, continuous scanning strategy is developed to rapidly acquire a stack of large-FOV images with three-dimensional (3-D) nanoscale shifts encoded. Then, by adopting a subvoxel-resolving procedure, the SLSM method models these low-resolution, cross-correlated images in the spatial domain and can iteratively recover a 3-D image with improved resolution throughout the sample. This technique can surpass the optical limit of a conventional light-sheet microscope by more than three times, with high acquisition speeds of gigavoxels per minute. By fast reconstruction of 3-D cultured cells, intact organs, and live embryos, SLSM method presents a convenient way to circumvent the trade-off between mapping large-scale tissue (>100 mm 3) and observing single cell (∼1-μm resolution). It also eliminates the need of complicated mechanical stitching or modulated illumination, using a simple light-sheet setup and fast graphics processing unit-based computation to achieve high-throughput, high-resolution 3-D microscopy, which could be tailored for a wide range of biomedical applications in pathology, histology, neuroscience, etc.
Underwater pressure sensors with high sensitivity over a broad pressure range are urgently required for the collection of valuable data on pressure changes associated with various wave motions. Here, a class of carbon-nanotube-based pressure sensors, which can be directly used in oceans without packaging, is reported. They use salt water as an electrolyte for electrochemically converting mechanical hydraulic energy into electrical energy and generating electrical signals in response to pressure changes in seawater. They can sense wave amplitudes from 1 mm (i.e., 10 Pa) to 30 m, which covers the range of almost all wave motions, and provide high stability during cycling in seawater. Also, they are self-powered and provide harvested gravimetric energy that is six orders of magnitude higher than that for commercial piezoelectric sensors for frequencies below 2 Hz (the range within most wave motion occurs), which has not been achieved before. These self-powered sensors operate from 4 to 60 °C and in direct contact with salt water having a wide range of salinities (from 0.1 to 5 mol L −1). Importantly, the unique electrochemical mechanism provides a new pressure sensing strategy to address the challenges in realizing high precision, low-frequency pressure measurements, and a broad detection range.
Capillary electrophoresis (CE) on microfabricated structures has achieved impressive sample throughput by combining fast separation speed and parallel operations. One obstacle to further increasing throughput has been lack of methods for loading and injecting individual samples at a rate that matches analysis speed. To address this issue, we have developed a microfluidic device in which samples stored as nanoliter volume plugs segmented by a fluorocarbon oil are introduced sequentially to an array of three electrophoresis channels. A microfluidic interface consisting of patterned surface chemistry and geometric restriction was used to extract samples from each segmented flow channel and transfer to the respective electrophoresis channel for separation. Fluorescence detection was achieved by imaging the chip using a fluorescence microscope equipped with a charge-coupled device. Characterization of the system shows that injection volume is controlled by sample plug volume, flow rate during introduction, and voltage applied to the electrophoresis channel. The system was tested for a GTPase assay. Peak area ratios of enzyme product and internal standard had 6% relative standard deviations. Cross-contamination between peaks was 7%. Throughput of 120 samples in 10 min was achieved. Further development of the system may allow application to high-throughput applications such as drug screening.
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